On 05/30/2013 04:14 AM, Dongxu Wang wrote: > Hi, > > Now block layer does not check whether backing_file chain can be a > circle, do you think it is necessary to do a check? > > For example, 1.qcow2's backing_file is 2.qcow2 and 2.qcow2's > backing_file is 1.qcow2, then any IO operation will be a fault. > > If necessary, I will post a patch to fix.
Yes, it's worth patching. > > [$] qemu-img create -f qcow2 1.qcow2 > qemu-img: Image creation needs a size parameter > [$] qemu-img create -f qcow2 1.qcow2 8M > Formatting '1.qcow2', fmt=qcow2 size=8388608 encryption=off > cluster_size=65536 lazy_refcounts=off > [$] qemu-img create -f qcow2 2.qcow2 -o backing_file=1.qcow2 > Formatting '2.qcow2', fmt=qcow2 size=8388608 backing_file='1.qcow2' > encryption=off cluster_size=65536 lazy_refcounts=off > [$] qemu-img create -f qcow2 1.qcow2 -o backing_file=2.qcow2 > Formatting '1.qcow2', fmt=qcow2 size=8388608 backing_file='2.qcow2' > encryption=off cluster_size=65536 lazy_refcounts=off > [$] qemu-io -c "read -v 0 512" 1.qcow2 > ^CSegmentation fault (core dumped) Also make sure that 'qemu-img info 1.qcow2' and 'qemu-img info --backing-chain 1.qcow2' don't crash. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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